This VB3A9 monoclonal antibody recognizes human latency-associated peptide (LAP), also known as the TGF-β propeptide. Human LAP is a homodimer of 65-75kDa that is non-covalently associated with TGF-β and this complex is also referred to as the small latent complex (SLC). LAP can be covalently associated with latent TGF-β binding proteins (LTBP) through disulfide bonds, forming the large latent complex (LLC). The association of LAP with TGF-β facilitates its secretion and also renders TGF-β inactive.

VB3A9 has been reported to cross-react with non-human primate LAP, but does not cross-react with mouse LAP.